US2405580A - Method for producing alkali metal oxides - Google Patents

Description

Aug. 13, 1946. c. B. JACKSON METHOD FOR PRODUCING ALKALI METAL OXIDES 'Filed nec. 14, 1940 INVENTOR. JACKSON j. if

CHREY E.

BY ArroR/VEK these'- layers to the oxidizing atmosphere:

Patented Aug. 13, 1946 CareyB.: Jackson,Forest Hills, Pa., assigner to'.

Mine Safetyv Appliances Company; Pittsburgh',

Application December 14, 1940", Ser'aLNo. 370,159'

(Cl. 23-184J 10 Claims'. l

This invention relates t'oa methodl of? manufacture of oxides-of metals, and-more particularly, to a method and apparatus which may be; used toproduce uniform-ly andf economicallyoxides of rn-et'al's;` such aspotassium orv sodium ora mixture thereofand the pro'duct of which is especially adaptable as an air purifying' and oxygen' evolving compound; One of the methods heretofore available for oxidizing these-alkali metals toa high exi-destato andv which method has had some commercial valueconsists of vatw'ostep or two-stage methodv of procedurea In this method, the pure metal is oxidized irst-to a compositionapproximatingxthe metal monoxide and' this is accomplished bysubjecting the surfaceof the-pure molten metalto ani oxidizing atmosphere; The oxygen content of the uid or atmosphere supplied is limited to less'than l0v per 'cent-because any-'greater amount Yvoul'd produce an explosive condition due tothe mass' involved the vapori pressure of the metall. The reaction itself is sufficiently ex'- othermic to carrythe: reaction to'com-pletionand this provides asource of danger 'if too' much mass invoved at one time. The high oxide orvperoxide, which inV thecase of"potassi`um is potassium tetraoxide (K202i)- and inthe case ofl sodium if'ssodiumperoxide (Na202), is then` formed from the monoxide' by subjecting the surface of the molten metal' monoxide toox-idizingiiuid. This reactionis not suiciently exoth'ermic tor` carry on the reaction and heat must besuppliodvr con-- tinuously. One of the principal di-culties inthis method is the fact that thereaction takes place slowly and it isj diiiicult to produce a uniform of heat mustV be continuously added tothe mass to oxidize' the metal to the highestV availableV oxide.

In orderV tra-expedite this type -ofoxidizing pro cedure, it has been suggested to supply the-molten`V metal inv theform of'y thin layersI and then subject Such procedure would, no doubt, improve the uniformity of the composition prepared, a great- 2 amount oi' time i's--stilly needed to complete the reaction and it necessitates the use ci` consideraktieI equipment if the product is to be manufactured" incommercial quantities;

The physical characteristics of the resulting productl of thisgeneral'methodiis dense and hard and unsuitable for' use in respiratory apparatus and no treatment hasbeen found which will make the-product ofr ay nat-ure that makes it suitable for this' purpose. In somel instances, the product formed is so'lzardv as to dissolve only slowly in Water, An air purifying composition,` in order't'o be useful iny respiratory-apparatus must be-of a porous-'nature or have such characteristics that it is instantly'reactive with respiredY air by being penetratie by 'carbon dioxide and Water to absorb carbon dioxide and toy evolve oxygenV to" replace to somev extent the; oxygen consumed.

The-principalobject voithis inventionl is to provide a-'method--off forming' an oxide of a metal' and' an apparatusA for performing the method which is continuous, simple in operation, inexpensive and rapid inperformance and commercially practicable and whichv is adaptable to produce potassium or'sodi-u-mperoxide or a nii-xture thereof of uniformj composition having defi-- nite physical characteristics rendering the product adaptableast an air purifyingcomposition,

'l'l'ie'f-method of' my' invention employs the treat-l ment off' molten metal- W- hich isto; be reasonably puI-e-y or at leastI not' containingany impurities which would interfere with the process or prevent its being used for the purpose intended.- The molten metal is made-to 'ow and in an atomized state to form a stream of small or minute par-` ticles and thisv stream isthen subjected to an oxidizing atmosphere.. This atomization steprenders-the' me tali'ncreasingly reactive and suiicien-tly so that a substantially uniform oxidized product isy produced in a rapid and inexpensive manner. In carrying out themethod for produc'- ing alkali peroxides, such as potassium peroxide, a small` stream of' molten metal is directed into a flow of iluid'` having an oxygen content of at least 1'3- per'cent by volume and preferablynot more than 35- per cent.' Within these limits of oxygen content, the method can be carried on to the best advantage relative to the rate of proiuction, uniformityA and protection of apparatus; Since the constituency of* ordinary atmosphere i's- Withinl the designate-d limits, it is suitable for the practice' of this method. By i-ntroducin'gja streaml of' themolten'metal into aiioW of air, fine spherical-likeparticles or globules of material are .fortified and suspended in the flow, and an indevice in a thin or ne stream of the molten metal and which when being directed into the fluid oW is dispersed so as to form finely divided particles of the molten metal, which operation will be hereinafter described as atomization. For the purpose of collecting the o-xidized metal, a receiving chamber 8 is directly connected to the atomizing device and it has a vent ilu/connected to the atmosphere so that an ordinary atmos- .pheric condition exists within the chamber and Va discharge 8b is provided in its lower extremity.

pleticn by this continuous process. ,7, .y i It was thought that any method based upo the atomization of such reactive metal as potassium and sodium would be dangerous in that the mixture of the metal with atmosphere would be dangerously explosive and thus any such hazards would render the method impractical for commercial purposes. It has been found that by controlling the oxygen content Within the limits set forth above, any such dangers are eliminated sufliciently provided some care is taken in the practice of the method and it can be and is being performed on a commercial scale, with inexpensive apparatus and at a low cost of operation.

In order to prevent the oxide from becoming hard and of a high density, it is cooled quickly by the flow of air and reduced below the fusion temperature of the oxide. Ordinarily, atomlzed molten metal when oxidized appears to burst open or explode .the spherical shape or globule type of particles, and when cooled it reassurnes this globule shape due to the surface tension of the material. This immediate cooling of the reacted material appears to Vcause it to remain in the bursted condition,rit being what might be termed frozen in this condition, and this physical condition is of an aborescent, or fluffy, nature in structure and because of this property is especially adaptable for respiration apparatus.

For the purpose of aiding in giving a full and complete description of the method, an apparatus is illustrated anddescribed which has been used for producing potassium tetra-oxide in commercial quantities. Referring to the drawing, the apparatus is simply a iluid spray device such as is used to apply paints or other coating on to surfaces and which has been found to be adaptable to discharge a thin or ne stream o f metal, this being controlled by an adiustment which forms a part of the device. The stream is diverted into an air flow which effects an atomization of the metal,

The device is made of a metal material which is not affected by the temperatures involved in this method and comprises a housing I having a passage 3 and a passage 4. These passages are connected to suitable tubes, which in turn are connected to a source of oxidizing iluid and to the molten metal, respectively. A vented receptacle contains the molten metal and a tube 4a connected to the passage 4 is inserted therein. An opening I is provided in the housing for the passage 4, while Van opening E Which is aligned With the opening 1 isprovided for the passage 3.

The oxidizing :duid under pressure is introduced into the housing through the passage and completely encircles the passage 4 containing the.

molten metal and by being discharged at a rela-Y tively high velocity at the opening-5 and over. the opening 1 is effective tol draw the molten metal up into the passage and against a needle adjustment 9. This adjustment controls the discharge of the metal particles from the device and by such the metal is discharged from the The op-eration of this device is not described in 'detail nor is the apparatus since it is a device wellv known inthe art and its principle of operai receptacle 5 is drawn into the passage 4 of the housing proper by the flow of oxidizing fluid, introduced into the passage 3, over the opening of the passage 4 or in such relation that the molten metal is discharged from the device in a small stream readily dispersable and into the stream of oxidizing iiuid producing the suction and carrying the formed metal particles or atomized stream of metal into the receiving chamber 8. The metalparticles are intimately mixed with the oxidizing fluid and because of this and the molten state of the metal as well as the heat evolved, an instant reaction oi the metal and the iiuid is caused to oxidize the metal completely to its highest state. No means or medium is required to initiate the reaction, since the molten metal Vparticles in the oxidizing iluid flow are instantaneously reactive. The heat evolved also accelerates the reaction and the excess of oxygen present causes the oxidation to be rapidly carried to completion. y

In employing this process in a commercial mannerto produce potassium tetra-oxide, it being understood that any reference to peroxide is to be-construed to mean the highest state of oxidation attainable and suitable for commercial use, the oxidizing uid flow is produced by connecting thepassage 3 o-f the housing to a source ot ordinaryv atmosphere or airat a'suiiiciently high pressure. In one instance, which has proven to be a commercial application, the air is at about 20 pounds pressure and at a temperature of about C. YThe potassium metal is heated to a molten state and maintained in this state during the performance of the method and is preferably at a temperature several degrees aboveits melting point. In any event, the temperature should be such that a slight reduction would not cause a solidication or Aany thickening of the molten metal and prevent its being readily and efficiently atomized or discharged in a stream atomized by impingement against a stream of air. For some purposes, it maybe advisable to provide some form of an'inert atmosphere over the surface ofthe metal contained in the receptacle 5 in order to prevent any contamination of the metal before it is introduced into the atomizing device.

By heating the compressed air to a temperature of about 75C., the metal within the housing I, or specifically within the passage 4, is main tained in a molten state while passing through the device. more or less ancillary because in using air for the scribedmanner.

However, this function of the air supplied is for the purpose of keeping the metal in a molten state at the time of discharge into the stream of oxidlizing iiuid. The heat in the molten metal is adequate to initiate the-oxidation and the Vheat evolved bythe reaction accelerates the rate." In all cases of application of my method, the chemical properties of the selected metalmust be considered in adapting my nventionto the metal. The properties of the metal upon' which the method depends are'known and the adaptation of my method to the selected metal can be made by those skilled in the art. By proper control of the dow of the molten metal and the oxidizing fluid, the`desir'ed oxidation product can be produced; However, the metal to be oxidized must be such that it can be atomized in a molten state and in-V termixed in 'an oxidizing iiowand which by atomization' becomes suiliciently reactive within the apparent limits of the invention to form the desired oxidation product.

One of the conditions that appears to lessen the hazards that exist in treating the highly reactive alkali metals is the vacuum that is utilized in atomizing the molten metal. It is apparent that if a positive pressure sufficient to move the metal to the point of discharge and then discharge it at a sufliciently high velocity is applied tothe metal and the metal under pressure introduced into a iiow of oxidizing uid that'some conditions might be created for certain metals which would result in avery hazardous condition' of operation. Consequently, this method of discharge of the metal is preferred although it is apparent that it is not indispensable in the practice of the method. This vacuum also eliminates any premature firing or ignition of the metal.

.-'It'is `intended that this detailed description of my method vas specicallyapplied to the oxidation of alkali metals, and particularly of potassium metal, discloses the principle involved and the exemplary vapparatus by which the methody can be carried on satisfactorily are what I now consider to be the best application lof 'my invention, but it is intended that the invention beV limited only by the scope of the appended -claims.

' I claim:

'1. That method of :making alkali metal ox-l .ide which comprises spraying'molten alkali metal into a current of an "atmosphere containing oxyi gen and a gas inert tosaid metal and thereby oxidizing the metal rapidly, and supplying said atmosphere in an amount such as' to'provide an excess of oxygen over that theoretically necessary for 'said oxidation and such, relative to its" a gas inert to said metal and heated tov a tem-- perature to maintain said metal molten and thereby oxidizingthe particlesof'metal rapidly to peroxide, and supplying said atmosphere in 8 an amount such as to' provide an excess of OXY- gen `over that theoretically necessary forA said oxidation and such, relative to its temperature, as to quench the oxideV below its melting point substantially as rapidly as it is formed, and thereby-producing the peroxide in a iiuiiy and uniformly oxidized form of low apparent density and of high reactivity with exhaled air. 4. A method according to claim 3, said atmosphere being air. V 5. That method of making alkali' metal per'- oxide which comprises atomizing molten alkali metal at a temperature above but close to its melting point into a current of air heated to a temperature to maintain the metal particles molten and'thereby rapidlyv oxidizing the metal particles to peroxide, and supplying said current of air in an amount such as to provide an excess of oxygen over that-theoretically necessary for said oxidation and such, relative to its temperature, as to quench the oxide below its melting point substantially as rapidly as it is formed, and therebyproducing the peroxide in a iluiy and uniformly oxidized form of low apparent density and of high reactivity with exhaled air.

6. 'A method of making potassium tetroxide according to claim 5, said metal being potassium, and the potassium and air being heated to about C.

7. That method ofv making alkali metal peroxide which comprises providing a body of at least one metal of the group consisting of sodium and potassium in the molten state, continuously atomizing the molten metal with a stream of gas' under pressure and containing from about 13 to about 35 per cent of oxygen and substantially all of the remainder inert to said metal, said gas being heated to a temperature to maintain said metal molten, and regulating said stream to provide an excess of oxygen over that theoretically necessary to convert said metal to theperoxide state and such, relative to its temperature, as to quench the peroxide-below its melting point substantially as rapidly as it is formed, and thereby producing the peroxide in a fluffy and uniformly oxidized form of low apparent density and ofhigh reactivity with exhaled air.

8. A method according'to claim 7, said metal being postassium and said peroxide being potassium tetroxide. Y

9. A method according to claim 7, said metal being potassium, said peroxide Vbeing potassium tetroxide, and said current of air being supplied in an amount such as to provide from about `5 to about l5 times the amount of oxygen theoretically necessary for oxidizing the metal.

. 10. That method of making peroxide of metal of the group consisting oi sodium and potassium which comprises spraying the molten metal in a current of an atmosphere of gas inert to the metal and containing oxygen into a chamber heated only by the heat liberated therefrom, supplying said atmosphere in an amount such as to provide oxygen in excess of that necessary for said oxidation and such, relative to its temperature, as to quenchv the peroxide formed below its melting point substantially as rapidly as it is formed, and thereby producing said oxide in a highly porous andA reactive form of low apparent density.

` CAREY B. JACKSON.

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